Millions of tons of coal ash are

produced worldwide each year.

EPRI and others have done

extensive studies over many years

of the nature of coal ash and its

possible effects on the

environment and human health.

This Environmental Focus feature summarizes

this information, applicable regulations that

govern the handling and use of coal ash, and

the benefits that can result from its use.

Coal Ash:I t s Or i g i n , D i s p o s a l , U s e , a n d P o t e n t i a lH e a l t h I s s u e s

What Is In Coal Ash? What Happens toPower Plant Coal Ash?

Potential Health Issues Environmental Concerns

Environmental Benefits

An issue report from EPRI's Environment Division

I N S I D E

When examined micro s c o p i c a l lymost fly ash particles are seen assolid or hollow spheres resemblingglass beads. These glassy spheresa re composed pre d o m i n a n t ly oamorphous material.

The Story in Brief

Coal ash consists of materials from the earth’s crust, oxidized by the

heat of combustion.

Health risks from coal ash are minimal, whether it is in the form of a

waste coal combustion by-product or a material used in construc-

tion products.

Studies have shown that although trace elements may leach from

coal ash in prolonged contact with the water table, they do not

migrate far from the ash site and are present at very low concentra-

tions, and therefore do not present a health threat.

The general public does not encounter coal ash in quantities that

might result in health risks. Power plants implement protection mea-

sures, such as wetting the ash to eliminate inhalation risks, and use

containment strategies and monitoring of wells to avoid risks from

ingestion. In extreme occupational settings, some power plant

workers could inhale harmful quantities of d ry ash part i c l e s . U n d e r

hese circumstances, OSHA precautions are recommended.

Radiation in fly ash and in products produced from fly ash is

minimal—well below EPA’s action standards.

Studies on various animals examining the toxic effects of ingesting fly

ash constituents have not found pathological damage that would

suggest potential human health problems.

Use of fly ash as a recycled material can have economically and

environmentally beneficial results.

ver half of the electricity produced in

the United States is generated from

coal—America’s most abundant fuel

resource.When coal is burned in a power

plant, it leaves behind ash—some of which

falls to the bottom of the furnace (bottom

ash) and some of which is carried upward

by the hot combustion gases of the furnace

(fly ash).To prevent fly ash from entering the

atmosphere, power plants use various col-

lection devices to gather it and keep it from

being carried with exhaust gases out the

stack.

In 1996,America’s coal-fired power plants

produced more than 53 million tons of fly

ash, bottom ash, and boiler slag (vitrified

bottom ash). Coal ash has physical and

chemical properties that make it useful for

construction and industrial materials.

Researchers continue to develop new appli-

cations for coal ash that allow it to be recy-

cled in greater quantities and in more

valuable ways. It is currently used in

roadbeds, structural fill, cement, concrete,

and flowable fill; for waste stabilization; and

as an alloying material for lightweight cast-

ings. However, when ash transportation costs

or other factors make commercial use

uneconomic, the ash is placed in engineered

landfills permitted by regulatory agencies.

Each of the various ash uses has been

studied for its engineering effectiveness and

for potential effects on human health and

the environment. Similarly, the environmental

integrity of coal ash disposal sites has been

evaluated extensively.This report outlines

the nature of coal ash, where the collected

fly and bottom ash go once they leave the

power plant, health and environmental infor-

mation, and applicable regulations.

O

3

What Happens to PowerPlant Coal Ash?

Coal Ash Landfills

Although the chemical and

physical properties of coal ash

make it ideal for a variety of

engineering applications, it must

compete against other inexpen-

sive bulk materials such as sand

and gravel, and therefore is eco-

nomic only where transporta-

tion and handling costs can be

kept low. As a result,about

three-quarters of the coal ash

produced in the United States is

not recycled for commercial

use, but rather is placed in spe-

c i a l ly designed, p e rmitted landfi l l s .

To prevent impacts on the surrounding envi-

ronment, modern coal ash landfill sites are

carefully selected.The selection process

involves topographic mapping, site reconnais-

sance, an environmental inventory, and

surface water and groundwater studies. Sites

on flood plains are generally avoided

because of potential erosion, as are those

near wetlands or on a drainage pathway to a

water body, where repeated water intrusion

could dissolve some trace elements.

Once a site is chosen, the landfill is con-

structed to be compatible with the local

What Is In Coal Ash?

Ash produced from coal-fired power plants

is much like volcanic ash. It consists of lime-

stone, iron, aluminum,silica sand, and clay—

essentially materials from the earth’s crust,

oxidized by the heat of combustion.1

In addition, coal ash contains trace quantities

(in the parts-per-million range) of the oxi-

dized forms of other naturally occurring ele-

ments.These same elements exist in soil,

rock,and coal. Such trace elements typically

include arsenic, boron, cadmium, chromium,

copper, lead, selenium, and zinc, which can

have adverse effects on human health if

inhaled or ingested in sufficient quantity. Coal

ash composition and mineralogy (including

its trace element content and form) vary

among power plants and are related pri-

marily to the source of the coal and the

combustion conditions.

The U.S. Environmental Protection Agency

(EPA) has reviewed extensive studies on

coal ash for health and environmental risks

and has examined coal ash samples col-

lected from power plants around the

country. In 1993, the agency determined that

power plant coal ash is nonhazardous and

should be regulated accordingly.2

Nevertheless, protective measures are gen-

erally used when fly ash is placed in disposal

sites, to prevent any trace elements that

could be mobilized by rain or other water

sources from reaching drinking water

sources.

terrain.Where the underlying natural soils

are very permeable, a clay or plastic liner

ensures that the ash does not come into

contact with the under lying groundwater.

Only small sections of the

landfill are open at a time

to limit the effects of

wind and rain. Once each

section is full,it may be

capped by low-perme-

ability clay to prevent

rainfall from entering.

Finally, wells are typically

installed around the site

so that the quality of sur-

rounding water can be

routinely checked to

determine whether any

ash constituents are

escaping from the site . Minor trace element

migration typically poses no concern, but a

large increase in concentration could indi-

cate the need for liner repairs.

Using Coal Ash

The table below lists the leading construc-

tion and industrial applications of power

plant coal ash.

Bottom ash, which is coarser than fly ash, is

used chiefly where its larger particle size is

an advantage, such as in blasting grit or

roofing shingle granules. Bottom ash is also

■ Autoclaved aerated concrete block

■ Hazardous waste or liquid fixation

■ Blasting grit

■ Highway ice control

■ Cement additive

■ Masonry blocks

■ Concrete admixture

■ Material in lightweight alloys

■ Concrete aggregate

■ Roadway/runway construction

■ Flowable fill material

■ Roofing granules

■ Grouting

■ Structural fill

Beneficial Uses of Coal Ash in the United States

Researchers continue

to develop new

applications for coal

ash that allow it to

be recycled in greater

quantities and in

more valuable ways.

produce aggregates for various l i g h t we i g h t

concrete products.

Fill for Highways and

Embankments

Coal fly ash is used as an

engineered material in

highway roadbeds and pave-

ments and as fill for embank-

ments.When applied for

these purposes,it is mois-

ture-controlled,compacted

as structural fill, and capped

with earth or other mate-

rials. In highway applications,

the asphalt or concrete

paving acts as a cap to prevent water from

coming into contact with the ash.

Embankment applications use interceptor

drains or other measures to route rainwater

or snowmelt drainage around the fill site.

Ash used in embankments is also typically

covered with topsoil to prevent erosion and

speed revegetation.

Flowable Fill

Coal fly ash can also be an ingredient in

flowable fill—a fluid, low-strength material

commonly supplied by ready-mix concrete

producers for backfill or structural fill needs.

It can easily be pumped from a truck and is

frequently used to fill irregular spaces. It is

sometimes used to fill aban-

doned mines to prevent

sinkholes or land subsidence

Fills containing coal ash can

help neutralize acids in mine

site ponds or excavated

areas.

Autocla ved Aerated

Concrete

Coal ash can replace sand in

autoclaved aerated concrete

(AAC) blocks, a puffed type

of solid concrete block

already used widely for building construction

throughout Europe and Asia.AAC blocks

can contain as much as 70% ash and are

l i g h t weight and strong, although they can be

cut with a saw and hold nails.They are also

fire and creep resistant and have good insu-

lating properties for both heat and sound.A s

A m e rican timber resources dwindle and

lumber prices ri s e, A AC is expected to

become an important commercial bu i l d i n g

m a t e rial in the United States. Ash-based A AC

blocks have been approved as a bu i l d i n g

m a t e rial by the building trade industry ’s

National Evaluation Service (NER-523).

Ashalloys

More recently, coal fly ash has been used as

an ingredient in “ashalloys”—blends of ash

and lightweight metals such as aluminum and

effective on roadways to hasten snow

melting and provide traction on icy pave-

ments. Some transportation agencies prefer

it over salt, which causes car bodies to

corrode and can harm vegetation. Its size

and drainage characteristics also make

bottom ash an excellent sub-base material

or buildings and parking lots.

Fly ash is lighter and more cementitious and

is used in a wide variety of applications.

Coal Ash in Concrete

Coal fly ash has been used around the

world as an ingredient in concrete for more

than 60 years. In fact, many U.S. concrete

suppliers routinely use fly ash in their con-

crete mixtures.The ancient Romans used a

similar substance—volcanic ash—to con-

struct the Coliseum and other structures

that still stand today, testaments to the dura-

bility of naturally cementitious ashes.

Coal fly ash processed into pellets can be

used as an aggregate in concrete, boosting

the overall fly ash content of the concrete.

Power plants in Florida and Wisconsin have

been operating pelletizing plants that

Coal fly ash has been

used around the

world as an

ingredient in

concrete for more

than 60 years.

Autoclaved aerated concrete blocks arelightweight and strong. They are widelyused as building material in Europeand Asia and have been approved foruse in the United States.

During operation of a coal-fired power

plant, some utility employees may be

exposed to appreciable amounts of fly ash,

either as suspended particulates or in col-

lected ash piles. Such personnel include pri-

marily ash haulers, ash silo operators, truck

loaders and drivers, ash system inspectors,

and ash collection system personnel.The

main sources of ash dust are the ash

transfer system and ash loading.An EPRI

study to determine potential health effects

of workers in frequent contact with coal fly

ash found that routine operating activities

did not produce hazardous exposures.4

Moreover, occupational

health records for these

types of workers do not

show a higher incidence

of respiratory problems

than those of powe r

plant wo rke rs who do

not wo rk as closely with

coal ash.

However, in some power

plant maintenance situa-

tions, airborne concen-

trations of total and

respirable particulate

could exceed Occupational Safety and

Health Administration (OSHA) permissible

limits for uncontrolled exposure.This level

of significant ash exposure can occur to

workers involved in planned plant mainte-

nance or repair, when workers can be

exposed to levels of ash particulates up to

10 times higher than the dose during

normal operation. Workers encountering

these conditions must use respirators or

other devices to prevent particle inhalation.

Similarly, workers “gritblasting” boiler tubes

or other equipment (the grit used is often

bottom ash) wear protective gear to

prevent inhalation of particles, in compliance

with applicable OSHA standards.5

5

magnesium.Ashalloy castings are advanta-

geous in weight- and cost-sensitive products

such as automobiles and trucks. EPRI is cur-

rently developing an ashalloy that would dis-

place some of the lead in lead-acid batteries

with coal ash. Such a lead ashalloy would

lighten batteries by 50%, expanding their

usefulness in electric vehicles by increasing

acceleration and range. It would also reduce

the environmental effects associated with

lead use.

Potential Health Issues

As with many substances, the recycling and

disposal of coal ash raises concerns about its

human health and ecological effects. Most

health-related questions about coal ash

center on the inhalation of ash particles,

ingestion of particles or dissolved trace ele-

ments, direct skin contact, or exposure to

minutely radioactive trace elements.

When evaluating potential health risks from

coal ash particles or constituents,

researchers assess mobility, changes in chem-

ical form over time or after coming into

contact with water, how individuals may be

exposed, and whether any plausible level of

exposure can adversely affect human health.

The following sections review these issues

and summarize the findings from relevant

research.

Ash Dust

People who do not work with coal ash

directly will not be exposed to a level of ash

particles that could produce health prob-

lems. Studies have shown that anyone not

handling dry, unprocessed ash directly is

extremely unlikely to be exposed to ash

dust at levels sufficient to elicit any response.

Likewise, exposure to compounds such as

arsenic and chromium, which can be present

in coal fly ash in minute quantities, is unlikely

to exceed background environmental expo-

sure (exposure levels occurring naturally in

the environment). Moreover, there are no

inhalation risks from products manufactured

with fly ash, such as houses made from AAC

blocks or roads made partly from coal ash.

Like any lightweight material, dry coal fly ash

can become airborne .To prevent it from

blowing during handling, utilities take precau-

tions such as adding water or thoroughly

mixing it with water and transporting it as a

slurry. Coal ash landfills are usually located at

the power plant or a short distance away.

Coal ash sold commercially is also often par-

tially processed on site.

Whenever the m a t e rial is

shipped off site, t rucks or ra i l

c a rs are covered to preve n t

the ash from escaping.

Direct inhalation of coal fly

ash can cause potential

health problems related

either to the presence of

particles in the lungs or to

specific substances in the

ash.Any adverse effects

from fly ash are more likely

to occur in the respiratory

tract than in the alimentary

canal, simply because the mechanisms in the

respiratory tract are less effective for

expelling these particles.3 Because ash parti-

cles are round, they are less likely to lodge in

lung tissues than particles from other

sources. Nonetheless, very small particles

(less than about 10 microns in diameter) can

seat themselves deep in the lung. Because

coal ash contains small amounts of sub-

stances that can ir ritate the lung, they can

initiate an inflammatory response. Irritation

can result in scarring of the lung tissue, or sil-

icosis. If these scars become widespread in

the lungs, they can hamper breathing.

People who do not work

with coal ash directly

will not be exposed to a

level of ash particles

that could produce

health problems.

EPRI has studied the

health and

environmental

effects of ash used in

various applications

over different

regions of the

country and

concluded that the

health risks from

ingesting ash are

generally minuscule.

Some power plant maintenance situations

can also produce airborne concentrations of

arsenic that exceed OSHA limits.A study

examining potential hazards found that the

highest arsenic concentrations were in

power plants burning bituminous coal from

the eastern United States. Many of the air-

borne fly ash particles were found to be in

the respirable size range . But even under

such conditions, properly clothed workers

wearing respirators were protected from

excessive exposures to airborne fly ash and

its hazardous constituents.6

The American Conference of Governmental

Industrial Hygienists (ACGIH) has recom-

mended an allowable exposure concentra-

tion of 10 mg/m3 of noncrystalline

(amorphous) silica as an 8-hour time-

weighted average in air. ACGIH believes that

at or below this concentration, even contin-

uous workday exposure will not adversely

affect health. It is highly unlikely that such

exposure levels would be reached outside of

an occupational situation.7

Leaching from Coal Ash Land

Applications

Coal ash particles are essentially insoluble

aluminosilicate glasses. However, trace sub-

stances on the ash surface may be soluble.

Water percolating through the ash could

leach (dissolve) these elements or possibly

liberate small ash particles.The dissolved ele-

ments or ash particles could potentially end

up in a drinking water source such as

groundwater, a river, or a lake.The sus-

pended particles would be removed by

normal filtration at a water treatment plant.

However, the dissolved elements could

potentially be ingested by drinking the water

Ye a rs of EPRI demonstrations have confi rmed the benefits of ash and sludge in highway backfi l l , e m b a n k m e n t s , and pavement base cours e s .

7

using valid leaching protocols when evalu-

ating complex inorganic materials such as

coal fly ash or products made using fly ash,

because complex chemical reactions that

occur can significantly impact the generation

of leachate.14 One study reported that,

based on ASTM-D and EPA toxicity charac-

teristic leaching procedure protocols,“…it is

anticipated that AAC would pose virtually

no hazard to human health and to the envi-

ronment at large whether used as construc-

tion blocks or other building units or in the

form of demolition or manufacturing

wastes.”15

The University of Pittsburgh conducted

environmental and physical testing of AAC

blocks supplied by six U.S. utilities.

Researchers concluded that in all cases,

leachate compositions of 17 different ele-

ments16 show fly ash AAC materials to be

nonhazardous and likely environmentally

benign. Microtox® toxicity of ASTM and acid

rain leachates showed no toxic effects

attributable to AAC materials.17 This result

may be due in part to the fact that for con-

crete applications, the fly ash (and any trace

elements it contains) are encased and

trapped or “fixed”in the hardened concrete

matrix, reducing their ability to leach.The

particle size of fly ash relative to cement

reduces the permeability of concrete.

that had percolated through the ash. EPRI

has studied the health and environmental

effects of ash used in various applications

over different regions of the country and

concluded that the health risks from

ingesting ash are generally minuscule.These

studies focused in particular on the process

of water seeping through ash and leaching

trace substances into groundwater.

Studies have shown that even where some

leaching of trace elements from coal ash has

occurred, its effects did not pose public

health risks. For example, leaching studies

conducted at a structural fill site in

Minnesota and an embankment in Illinois

indicated some groundwater contamination.

However, nearly eight years after ash was

used to backfill the low-lying area of the

Minnesota site, sampling and analysis of sub-

surface waters showed only very small and

localized changes in trace element concen-

trations, and none was off site.

Concentrations of all trace elements in

water samples collected near the ash

deposit were under detection limits or

unchanged from background water quality

measurements. Only groundwater wells

located directly beneath the ash deposit

showed elevated concentrations of a few

elements.8 Even then, none of these con-

stituents migrated into the deeper ground-

water zone (a potential drinking water

source) or groundwater outside the ash fill.9

Similarly, nearly 15 years after ash was used

to construct a highway overpass embank-

ment in Illinois, sampling and analysis of

groundwater, soils, and vegetation showed

only slightly elevated levels of some con-

stituents related to ash.However,

researchers concluded that there was little

evidence of accumulation of ash-derived

chemicals in sandy soils beneath the ash.

Trace elements such as arsenic, selenium,

chromium, cadmium, and vanadium did not

migrate to groundwater. Shallow ground-

water wells located directly below the ash

and a short distance downslope of the

embankment found elevated concentrations

of some substances10 compared with

upslope wells; however, concentrations of

these chemicals were much lower in the

deeper wells below the site .11

Results from studies at five other road con-

struction sites in Georgia, Pennsylvania,

Arkansas,Kansas, and Arizona showed even

fewer environmental effects.At all sites,

regardless of age (7-17 years), climate, and

soil type, the effect from chemicals leached

from the coal ash was limited to the soil

immediately below

(0-6 ft) the roadbase or embankment.12

What accounts for the differences between

the sites in Minnesota and Illinois and the

other sites? Researchers believe they are

due largely to structural and hydrologic

factors. They observed that coal ash prod-

ucts used in areas with generally acidic soils,

shallow groundwater, and humid climates are

most likely to leach soluble constituents.13

Potential environmental impacts from the

h i g h - volume use of coal ash can be preve n t e d

by using only sites that have the proper stru c-

t u ral and hy d r o g e o l o g i c a l

c h a ra c t e ri s t i c s .

Leaching from

Products Containing

Coal Ash

Numerous studies on

autoclaved aerated con-

crete (AAC) have con-

cluded that it poses no

health threats from

leaching. Researchers did

note the importance of Typical coal ash impoundment pond.

ASTM: The American Society for Testing and Materials.

Autocla ved aerated concrete (AAC): AAC is a lightweight

concrete with no coarse aggregate that is produced by mixing

portland cement, lime, aluminum powder, and water with a

large proportion of a silica-rich material such as sand or fly ash.

Fly ash can be as much as 75% of the material by weight.AAC

combines relatively low thermal conductivity with mechanical

properties sufficient for many load-bearing applications. It is also

known as autoclaved cellular concrete (ACC) and porous

concrete.

Coal bottom ash: Ash from coal combustion that falls to the

bottom of the furnace.

Coal fly ash: Ash from coal combustion that rises with the heat

from the furnace and is caught and collected for reuse or

landfill.

Curie (Ci) :The unit of radioactivity of a material.Equal to

3.7x1010 disintegrations per second.

EPRI: EPRI creates science and technology solutions for the global

energy and energy services industry. Located in California in

the heart of the Silicon Valley, EPRI provides a wide range of

innovative products and services to more than 700 energy-

related organizations in 40 countries. EPRI's multidisciplinary

team of scientists and engineers draws on a worldwide

network of technical and business expertise to help solve

today's toughest energy and environmental problems.

Flowable fill: A fluid, low-strength material that can be used for

backfill or structural fill needs, referred to as controlled low-

strength material (CLSM) by the American Concrete Institute.

Flue gas desulfurization: A variety of flue gas cleaning

processes for controlling sulfur dioxide emissions from power

plants.

Landfill: A method for disposing of solid wastes by burying them

in layers of earth.

Leaching: The process of dissolving selected materials in solids by

contact with water, similar to running water through ground

beans to brew coffee . Coal ash studies have examined the

potential leaching of trace elements from the ash.

Microto x®: Aquatic test systems produced by AZUR

Environmental that indicate potential toxicity to humans.

Millirem (mrem): 1/1000 of a rem, which is an acronym for

Roentgen Equivalent Man.A millirem is a measurement of a

quantity of radiation that produces the same biological effect as

1 rad of x-rays or gamma radiation.

OSHA: Occupational Safety and Health Administration, an agency

of the U.S. Department of Labor.

pH: A measure of the acidity or alkalinity of a substance, with 7

being neutral (distilled water), 1 representing an extremely

acidic substance, and 14 representing an extremely alkaline

substance.

Picocurie: 1x10-12 curies (see curie).

Portland cement: The common name for commercial cement.

Radionuclide: A radioactive nuclide, or atom.

Radon: A naturally occurring inert gas created by the radioactive

decay of uranium-238, uranium-235, and thorium-232.

Trace element: An element present in extremely small

quantities. In coal ash, trace elements are typically metals.

GLOSSARY

Regulatory Status

In 1993,EPA determined that high-

volume coal combustion wastes should

be regulated as nonhazardous waste

under Subtitle D of the Resource

Recovery and Conservation Act

(RCRA),not under Subtitle C, which

covers hazardous waste.

A U.S. Geological Survey (USGS) fact

sheet states that “Standardized tests of

the leachability of toxic trace elements

such as arsenic , selenium, lead,and

mercury from fly ash show that the

amounts dissolved are sufficiently low

to justify regulatory classification of fly

ash as nonhazardous solid waste.”22

Other regulations and standards

regarding the use and disposition of

coal ash are in place, and vary by appli-

cation and from state to state.

9

Therefore, even if concrete were used in

ery wet soils or underwater, leaching would

be insignificant.

Many studies have examined the toxic

effects on various animals from ingesting fly

ash constituents,18 and none has suggested

associated health problems. Some tests have

shown slightly elevated levels of some ele-

ments in blood and various organs, while

others have found no increase. None of the

tests has revealed any damage that would

suggest an increased risk of developing

health problems from plausible exposure

levels.

Skin Contact with Ash

Most people never touch coal ash. Skin

contact is generally limited to power plant

workers and those who produce cement,

concrete, AAC, or some other ash-based

product. However, some highway depart-

ments use bottom ash for snow and ice

control,leaving deposits on roads and in

gutters where people or their pets might

touch it or track it into their houses. Based

on the experience of those who work

closely with i t ,a d ve rse health effects from

kin contact with coal ash appear to be

e x t r e m e ly unlike ly.

Radioactivity of Coal Ash

Coal,like all natural substances from the

Earth, undergoes a long-term process of

decomposition, and in doing so emits back-

ground radiation. We are exposed to the

Earth’s background radiation continually

throughout our lives. Because coal emits

natural radioactivity as a mineral, its ash does

as well.

EPA considers coal ash to be a diffuse

naturally occurring radioactive material

(NORM)—its most benign classification. In

March 1998, EPA issued a final rule stating

that radionuclides from all coal and coal ash

piles need not be reported under the

Comprehensive Environmental Response,

Compensation, and Liability Act (CERCLA,

or Superfund) or Emergency Planning and

Community Right-to-Know Act (EPCRA)

requirements. EPA’s decision was based on

the low risks posed by radionuclide releases

from coal and coal ash piles, which they con-

sidered to be “…within the range of ‘typical’

background concentrations in surface rocks

and soils in the U.S.”19

The U.S. Geological Sur vey (USGS) concurs.

In a recent publication, it states that

“Radioactive elements in coal and fly ash

should not be sources of alarm.The vast

majority of coal and the majority of fly ash

are not significantly enriched in radioactive

elements, or in associated radioactivity, com-

pared with common soils or rocks.” 20 They

also observed that “…no obvious evidence

of surface enrichment of uranium has been

found in the hundreds of fly ash particles

examined by USGS researchers.”

The radioactivity of a substance can be

described in two ways: in terms of its biolog-

ical effect on a human body (rem) or in

terms of the amount of radioactivity it emits

(curie). More often, the terms millirem

(mrem,1x10-3 rem) and picocurie

(pCi, 1x10-12 curie) are used.

The U.S. Nuclear Regulatory Commission

(NRC) has established a radiation dose limit

for the public of less than 100 mrem in a

calendar year from all sources.21 An industry

study calculated the radium concentration in

coal ash that would be needed to produce

an individual exposure level of 25 mrem per

year (one-fourth of the NRC limit). Results

indicated that “…in order to reach this level,

the concentration of radium in coal ash

(measured in picocuries per gram [pCi/g])

would have to exceed by orders of magni-

10

tude the highest radium concentrations ever

ound to be present.”23

The U.S. Department of Energy estimated

the radium concentration of fly ash to be no

more than 3.0 pCi/g.24 Even if the coal ash

contained 5 pCi/g concentrations,the dose

received by the workers most exposed to

coal ash would be well below 25 mrem

annually.25 In fact, mathematical modeling of

an ash pile showed that the dose received by

someone working with that ash is extremely

low—less than 0.0005 mrem per year. Doses

to the general public are even lower.26

Limited studies have been conducted to

quantify levels of radiation in water that has

leached through fly ash.According to USGS,

“… preliminary results indicate that concen-

trations are typically below the current [EPA]

drinking water standard for radium

(5 picocuries per liter [pCi/L]) or the initially

proposed drinking water standard for

uranium of 20 parts per billion.”27

Radon emissions from products made from

y ash are also low. USGS reports that “…

the radioactivity of typical fly ash is not signif-

icantly different from that of more conven-

tional concrete additives or other building

materials such as granite or red brick.”28

Measured emission rates from AAC blocks

made from fly ash from different electric utili-

ties have resulted in a radon equilibrium con-

centration in the range of 0.1–0.9 pCi/L. For

comparison, the EPA “action level” for radon

in indoor air spaces is 4 pCi/L.29 Overall,

based on radon studies,AAC appears to

pose virtually no hazard to the general public

or the environment, whether it is used as

construction blocks or other building units or

in the form of demolition or manufacturing

wastes.30

The only potential, remote

hazard from coal ash radioac-

tivity may be to wor kers in

lignite-coal-fired plants,where

one study found that radionu-

clide concentrations occasion-

ally exceeded NRC health

standards.31

EnvironmentalConcerns

Overall, coal ash poses a

minimal risk to plants and

animals.As noted previously, it

consists chiefly of common

compounds found in the

earth. For accepted practices

of disposal,transportation, and use, effects

from trace metal leaching and inhalation of

ash are both localized and minimal, as shown

in human health studies.

Studies of the effects of fly ash in lakes and

streams have also been conducted, even

though significant amounts of ash are not

found in public water bodies.These studies

showed that fly ash can adversely affect

aquatic life if it is present in sufficient quanti-

ties, mostly because of increased turbidity of

the water (which inhibits plant growth), gill

clogging, and increased alkalinity.

The pH of coal ash commonly ranges from 7

(neutral) to as much as 12 (alkaline). Plants

have difficulty growing in coal ash with a pH

in the upper end of this range (~10-12).

Coal ash has been extensively studied as a

soil amendment; researchers have found that

bottom ash can improve soil drainage and

that some coal ash can be used to provide

nutrients for plant growth. Used alone as a

soil, however, fly ash can have drawbacks:

aggregate instability, a tendency to erode,

nitrogen deficiencies and

availability, boron phytotoxi-

city, and low cation nutrient

retention capacity.32

Studies have also found that

the trace metals in coal ash

can be absorbed by vegeta-

tion.At the Minnesota road

site mentioned previously,

“vegetation samples growing

directly on the ash fill

showed an accumulation of

boron, magnesium, and

molybdenum as well as a

reduction in phosphorus.”33

The Illinois site also showed

similar results, but with a

reduction in magnesium.34 Nearly 15 years

after ash was used, soils and vegetation

showed localized changes due to leaching of

ash constituents. Because plants grown on fly

ash can absorb trace elements, care is

needed in determining appropriate applica-

tion rates when ash is used as a soil amend-

ment.A proper soil/ash mixture has been

shown to be beneficial for certain crops.35

Environmental Benefits

Recycling coal ash in products and construc-

tion applications can bring environmental

benefits.A recent study concluded that using

coal ash as a cement in concrete production

consumes less electricity and limestone than

does production of conventional cement.36

Avoiding electricity production lessens overall

emissions. Further, carbon dioxide and other

emissions from cement kiln firing are avoided

in direct proportion to the percentage of ash

substituted.

Used as a flowable fill for abandoned mines

(often in combination with flue gas desulfur-

A recent study

concluded that using

coal ash as a cement

in concrete

production consumes

less electricity and

limestone than does

production of

conventional cement.

11

ization by-products), coal ash prevents soil

subsidence and neutralizes acid mine

drainage. In an underground mine site

where coal ash slurry was placed for subsi-

dence abatement, environmental monitoring

showed a reduction of heavy metal

leachates,which was attributed to the neu-

tralizing effects of the ash slurry.37

Summary

When handled and disposed of properly,

coal ash does not present a public health or

environmental threat. Moreover, use of coal

ash as a recycled material in a variety of

applications has economical and environ-

mentally beneficial impacts, which can

reduce energy costs and emissions, provide

important materials for infrastructure and

uildings,and reduce land disposal needs.

1 EPA Guideline for Purchasing Cement and

Concrete Containing Fly Ash, Environmental

Fact Sheet, U.S. Environmental Protection

Agency, EPA/530-SW-91-086, January

1992.2 Final Regulatory Determination on Four

Large-Volume Wastes from the Combustion

of Coal by Electric Utility Power Plants, 58

FR 42466,August 9,1993.3 Coal Fly Ash:A Review of the Literature and

Proposed Classification System with

Emphasis on Environmental Impacts ,

William R. Roy, et al., Illinois Institute of

Natural Resources, State Geological

Survey Division,April 1981.4 Fly Ash Exposure in Coal-Fired Power Plants,

EPRI,TR-102576,August 1993.5 For further information on preventing

worker-related silicosis, see Silica Dust

Exposures Can Cause Silicosis ,

Occupational Safety and Health

Administration, OSHA 96-54 January 1,

1996.6 Ibid.7 Threshold Limit Values for Chemical

Substances and Physical A g e n t s. B i o l o g i c a l

Exposure Indices. A m e rican Conference of

G ove rnmental Industrial Hygienists:AC G I H ,

O H , p. 3 5 ,1 9 9 7 .8 Sulfate, boron, calcium, manganese,

molybdenum, and strontium.9 E nvironmental Pe r fo rmance Assessment of

Coal Ash Use Sites: Little Canada Stru c t u ra l

Ash Fill, E N-6 5 3 2 , E P R I ,M ay 1990.10 Boron, calcium, fluoride, iron, molybde-

num, potassium,lithium, silicon, strontium,

and sulfate.11 Environmental Performance Assessment of

Coal Ash Use Sites:Waukegan Ash

Embankment, EN-6533, EPRI, December

1990.

12 Environmental Performance Assessment of

Coal Combustion Byproduct Use Sites: Road

Construction Applications, TR-105127, EPRI,

June 1995.13 Ibid.14 Demonstration of Ash Utilization in the

State of North Dakota, EPRI,TR-106516,

March 1996. Section 8.15 Environmental and Physical Properties of

Autoclaved Cellular Concrete: Volume 1:

Narrative and Radon Exhalation Study and

Appendix A, EPRI,TR-105821,October

1996.16 Ag,Al,As, Ba, Be, Ca, Cd, Cr, Cu, Fe, Hg,

Mo, Mn, Ni, Pb, Se, and Zn.17 Environmental and Physical Properties of

Autoclaved Cellular Concrete: Volume 1:

Narrative and Radon Exhalation Study and

Appendix A, EPRI,TR-105821, p. vi,

October 1996.18 Coal Fly Ash:A Review of the Literature and

Proposed Classification System with

Emphasis on Environmental Impacts ,

William R. Roy, et at., Illinois Institute of

Natural Resources, State Geological

Survey Division,April 1981.19 63 FR 13463.20 Radioactive Elements in Coal and Fly Ash:

Abundance, Forms, and Environmental

Significance, USGS, Fact Sheet FS-163-97,

October 1997.21 10 C.F.R. Part 20.22 Radioactive Elements in Coal and Fly Ash:

Abundance, Forms, and Environmental

Significance, USGS, Fact Sheet FS-163-97,

October 1997.23 Assessment of NORM Concentrations in

Coal Ash and Exposure to Workers and

Members of the Public, Radian

Corporation, for the Utility Solid Waste

Activities Group, p. iv, June 1988.

Notes

E nvironmental Focus is published by EPRI, the research arm of the electric utility industry. For extra copies, contact Shannon Smith, (650) 855-1047 (ssmith@epri . c o m ) .

© 1998,EPRI,Inc.,EPRI,and EPRIWeb are registered service marks of EPRI,Inc., P.O. Box 10412, Palo Alto, CA 94303.

P rinted with soya ink on recycled paper (50% recycled fi b e r, including 10% postconsumer waste). P rinted in the United States of A m e ri c a .

EPRI 3412 Hillview Avenue, P.O. Box 10412,Palo Alto, California 94303 800.313.EPRI or 650.855.2000 www.epri.com

BR-111026

For More Information

To learn more about coal ash,

contact:

Dean M.Golden

Groundwater Protection/Combustion

By-Product Management

Environment Division

(650) 855-2516

e-mail: dgolden@epri.com

Dr. George Offen

Combustion By-Product Use

Energy Conversion Division

(650) 855-8942

e-mail: goffen@epri.com

Other Resources

American Coal Ash Association

(ACAA)

Samuel S.Tyson

Executive Director

(703) 317-2400

e-mail: ACAA-Tyson@msn.com

24 Integrated Data Base Report—1996: U.S. Spent Nuclear Fuel and Radioactive Waste

Inventories, Projections, and Characteristics; U.S. Department of Energy, Rev. 13,Table 7.6,

December 1997.25 Assessment of NORM Concentrations in Coal Ash and Exposure to Workers and Members of

the Public, Radian Corporation, for the Utility Solid Waste Activities Group, p. iv, June 1988.26 Ibid.27 Radioactive Elements in Coal and Fly Ash:Abundance, Forms, and Environmental Significance,

USGS, Fact Sheet FS-163-97, October 1997.28 Ibid.29 Environmental and Physical Properties of Autoclaved Cellular Concrete:Volume 1: Narrative and

Radon Exhalation Study and Appendix A, EPRI,TR-105821,October 1996.30 Ibid.31 Ibid.32 Coal Fly Ash:A Review of the Literature and Proposed Classification System with Emphasis on

Environmental Impacts, William R. Roy, et al., Illinois Institute of Natural Resources, State

Geological Survey Division,April 1981.33 Environmental Performance Assessment of Coal Ash Use Sites: Little Canada Structural Ash Fill,

EN-6532, EPRI,May 1990.34 Environmental Performance Assessment of Coal Ash Use Sites:Waukegan Ash Embankment,

EN-6533, EPRI, December 1990.35 Land Application Uses for Dry Flue Gas Desulfurization By-Products, TR-105264, July 1995.36 Analysis of Coal Ash Uses Before and After the EPA’s Nitrogen Oxides Emission Reduction

Program Takes Effect Using the Life Cycle Assessment Approach, American Coal Ash

Association/Ecobalance, Inc. (May/June 1997).37 Demonstration of Ash Utilization in the State of North Dakota, EPRI,TR-106516, March 1996.

Notes (continued)